Reverse explosion with voxels
From this answer, I've changed or set the following:



1- Keyed object
2- Particle
3- Surrounding sphere (viewed as bounds)
4- Bunny (viewed as bounds)

On the right the setting for keyed object (the 2nd PS has 10 for the time parameter).



Above the setting for the surrounding sphere (250 for the 'end' parameter).

And below the setting for the bunny: